<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* div+p{
      color: red;
    }
    div~p{
      color: blue;
    }
    div,p{
      background: forestgreen;
    } */



    /* li:nth-child(2n+1){
      color: red;
    } */


    /* li:first-of-type{
      color: red;
    } */


    /* div:before{
      content: 'before';
      color: red;
      font-size: 20px;
    } */

    /* div:active{
      background: red;
    } */


    /* a{
      color: red;
    } */
    /* [href]{
      color: orange;
    } */

    /* [href^=http]{
      color: orange;
    } */

    /* [href$=com]{
      color: orange;
    } */

    /* [href*=s]{
      color: orange;
    } */
    /* [href='http://www.baidu.com']{
      color: orange;
    } */
    /* a.snail{
      color: red;
    } */

    /* [href$='com'].snail{
      color: red;
    } */

    #box p{
      color: red;
    }

    .content{
      color: blue !important;
    }

    #content{
      color: orange;
    }

  </style>
</head>
<body>
  <!-- <p>div前面的p</p>
  <div>
    div标签
  </div>
  <h1></h1>
  <p>p标签</p> -->

  <!-- <ul>
    <p>p标签</p>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
  </ul>
  <ol>
    <li></li>
    <li></li>
    <li></li>
  </ol> -->


  <!-- <div>
    内容
  </div> -->

  <!-- <a>没有href</a>
  <a href="">空的href</a>
  <a href="http://www.baidu.com">http://www.baidu.com</a>
  <a href="http://www.sina.com">http://www.sina.com</a>
  <a class="snail" href="snail.com">snail.com</a>
  <a class="snail" href="snail.cn">snail.cn</a> -->



  <div id="box">
    <p class="content" id="content">内容</p>
  </div>
  


</body>
</html>